Originally, the term “battery” described a plurality of series-connected electrochemical cells. Today, individual electrochemical cells (individual cells) are also frequently described as batteries. During discharging an electrochemical cell, an energy-releasing chemical reaction occurs that is comprised of two electrically associated, but spatially separated sub-reactions. On the negative electrode, electrons are released in an oxidation process, resulting in an electron stream flowing via an external load to the positive electrode, which takes up a corresponding quantity of electrons. A reduction process thus occurs on the positive electrode. At the same time, an ion stream corresponding to the electrode reaction is generated within the cell. This ion stream is supported by an ion-conducting electrolyte. In secondary cells and batteries, this discharge reaction is reversible, and the option is therefore available for reversal of the conversion of chemical energy into electrical energy, which occurs during discharging.
Among known secondary batteries, comparatively high energy densities are specifically achieved by lithium-ion batteries, i.e., batteries in which lithium ions migrate from one electrode to the other during charging and discharging processes. Batteries of that type are suitable for use in portable devices such as mobile telephones and notebook computers. However, they are also specifically appropriate as an energy source for motor vehicles.
Lithium-ion batteries for motor vehicles frequently comprise a prismatic metal housing. The housing is customarily comprised of a container with a rectangular base and four side walls arranged at right-angles thereto, together with a cover, which is essentially of the same size and shape as the base. In general, the cover shows virtually no contours, and can be described as virtually flat. In general, the housing is closed, wherein the edges of the cover are bonded to the opening edge of the container.
In general, at least one individual cell is arranged in the metal housing. This can be present in the form of a cell stack (stack) of a plurality of flat individual cells, or in the form of one or more wound individual cells (coil).
Stationary components of a battery generally include a positive and a negative terminal stud routed through the cover, the base or a wall of the housing, and are electrically insulated from the housing by an electrical insulator. The region of a battery housing in which a terminal stud is routed through the wall, including the electrical insulator, is commonly described as a terminal feed-through. Positive terminal studs are electrically bonded to the positive electrode(s) of the at least one individual cell. Negative terminal studs are electrically bonded to the negative electrode(s) of the at least one individual cell.
Sealing the housing in the region in which terminal studs are fed through the wall is of particular significance. Glass compounds of the type described in DE 100 47 206 A1 are appropriate for sealing, for example, and simultaneously assume the function of an electrical insulator. Moreover, polymer-based sealing systems are also specifically appropriate.
Highly stringent requirements apply to a sealing system for a terminal feed-through. In addition to an outstanding insulation and sealing performance, the following additional properties are also of particular significance:                long-term mechanical stability in response to application of external forces to terminal studs,        thermal stability of −40° C. to +100° C.,        resistance to cyclic temperature stress, and        chemical resistance to various electrolyte systems.        
In general, sealing systems for terminal feed-throughs should have a minimum service life of 15 years. In the above-mentioned known sealing systems, this is not always the case. Plastic-based sealing materials are subject to embrittlement in response to long-term mechanical and chemical loading, and are consequently susceptible to stress cracking and sealing failure. Glass-based sealing materials frequently have a low elasticity and, consequently, a limited tolerance to mechanical moment loads. Abrupt application of forces can easily result in cracks, and likewise in the consequent failure of sealing.
It could therefore be helpful to provide batteries distinguished by terminal feed-throughs which fulfil the above-mentioned requirements more effectively than known solutions.